This invention relates to an internal combustion engine having an exhaust gas feedback conduit which extends from the exhaust conduit and which opens into the gas intake conduit upstream of an output setting member, such as a butterfly throttle valve.
In order to reduce pollutants in exhaust gases of internal combustion engines, particularly those used as power plants for automotive vehicles and, at the same time, to effect an improved utilization of the fuel, it is known to reintroduce the exhaust gases into the combustion process, that is, into the combustion chambers of the internal combustion engine.
A particular problem involved in the feedback of exhaust gases concerns a proper metering of the returned exhaust gases since, understandably, a constant exhaust gas quantity cannot be fed back into the combustion process over the entire operational range of the engine, that is, from idling run to full load.
In some arrangements, as disclosed, for example, in U.S. Pat. No. 4,079,710, the exhaust gas feedback conduit merges into the suction pipe (fresh gas intake conduit) downstream of the throttle valve (butterfly valve) which is connected with the accelerator pedal and which constitutes output setting member. On the other hand, according to U.S. Pat. No. 4,223,650, the exhaust gas feedback conduit merges into the suction pipe upstream of the output setting member and has the advantage that additional valves in the exhaust gas feedback conduit may be dispensed with. Although, as taught in the last-named U.S. patent, by virtue of positioning the inlet of the exhaust gas feedback conduit in the narrowest cross-sectional area of a venturi arranged upstream of the air filter of the engine, a certain relationship between the returned exhaust gas quantity and the inflowing fresh gas may be achieved without the need of additional valves (which would be actuated, for example, by the pressure in the suction pipe), it has been found that this solution does not take into account the requirements of current internal combustion engines.
Therefore, as disclosed in German Offenlegungsschrift (non-examined published patent application) No. 2,655,991, in order to increase the fed back exhaust gas quantities, it has been attempted to increase the pressure ratios and pressure differences--which determine the returned exhaust gas quantities--by placing the outlet of the exhaust gas feedback conduit in the intake gas conduit between two butterfly valves which are synchronously operated by the accelerator pedal. This arrangement, however, also does not take into account to a satisfactory extent the conditions in the internal combustion engine for the different operational modes or states.
To round out the state of the prior art, reference is further made to European Patent No. 89,492 which describes an internal combustion engine having two output setting members arranged serially in the intake gas conduit. One of the setting members is conventionally coupled with the accelerator pedal, while the other setting member is moved by a setting motor which is controlled electronically as a function of several operational parameters of the internal combustion engine and the vehicle. Such an engine design having two output setting members, one operated by the driver of the vehicle and the other moved as a function of operational parameters is intended to reduce fuel consumption; an exhaust gas feedback is not intended.